Two studies are reported related to musical instrument timbre qualia. In the first study, open-ended interviews were conducted with 23 musicians who were asked to describe their phenomenal experiences of imagined sounds for 20 Western instruments. A content analysis of the transcribed interviews suggests 77 qualitative categories underlying the musicians’ descriptions. In a second study, 460 musician participants rated subsets of the same 20 imagined instrument sounds according to the 77 categories derived from Study 1. Principal component analyses were applied to the results of Study 2, yielding several models. Researcher interpretations of the components in these models were combined with the results of supplementary polls where musicians rated the descriptive utility of each candidate component, producing a final 20-dimensional timbre qualia model. The model dimensions include rumbling/low, soft/singing, watery/fluid, direct/loud, nasal/reedy, shrill/noisy, percussive, pure/clear, brassy/metallic, raspy/grainy, ringing/long decay, sparkling/brilliant, airy/breathy, resonant/vibrant, hollow, woody, muted/veiled, sustained/even, open, and focused/compact.